Fetus

Fetal Heart Tracing

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Fetal Heart Tracing, Fetal Heart Tones, Fetal Heart Rate, FHR, FHT, Intrapartum Fetal Monitoring, Reassuring Fetal Heart Tracing, Non-reassuring Fetal Heart Tracing, Ominous Fetal Heart Tracing, NICHD Category, National Institute of Child Health and Human Development Category

  • See Also
  1. Fetal Assessment
  2. Fetal Testing Indications
  3. Continuous Electronic Fetal Monitoring (CEFM)
  4. Structured Intermittent Auscultation (SIA)
  5. Fetal Distress
  • Types
  • Intrapartum Fetal Monitoring
  1. Continuous Electronic Fetal Monitoring (CEFM)
    1. Indications
      1. High risk pregnancy (see efficacy below)
      2. See Peripartum Risk to the Fetus
      3. External monitoring is not possible
        1. Maternal body habitus
        2. Fetal Position interferes with monitoring
    2. Adverse Effects
      1. Requires Amniotomy
      2. Internal monitors increase risk of Chorioamnionitis, vertical transmission HSV and Viral Hepatitis
      3. Limits mobility of mother
    3. Efficacy
      1. CEFM does improve identification of Fetal Hypoxia
      2. CEFM does not significantly improve fetal outcome in low risk pregnancy
      3. CEFM increases the risk of surgical intervention (False Positive for fetal acidosis in two thirds of cases)
        1. Do NOT use CEFM as the only diagnostic tool indication for intervention
  2. Structured Intermittent Auscultation (SIA)
    1. Indications
      1. Low risk pregnancy
    2. Requirements
      1. Requires one-to-one nursing (every 5 to 15 minute monitoring) with nurses skilled in FHR auscultation
      2. Nurses must be able to palpate contractions
      3. Non-reassuring findings require clinical evaluation
    3. Efficacy
      1. Decreased rate of cesarean and operative Vaginal Delivery
      2. No increase in unfavorable outcomes compared with Continuous Electronic Fetal Monitoring (CEFM) in low risk patients
  3. Other intrapartum monitoring measures that are not often performed
    1. Fetal Scalp pH Sampling
      1. Prolonged sample to result time (approaches 18 minutes)
      2. Inadequate sample rate as high as 10%
    2. Fetal lactate scalp sampling
      1. Rapid turn around (2 minutes), but does not alter newborn outcomes
      2. East (2015) Cochrane Database Syst Rev (5):CD006174 [PubMed]
    3. Fetal Pulse Oximetry
      1. Decreases second stage operative Vaginal Delivery rates
      2. Does not alter newborn outcomes
      3. East (2006) Am J Obstet Gynecol 194(3): 606.e1-606.e16 [PubMed]
    4. Fetal Electrocardiograms
      1. Does not alter newborn outcomes
      2. No change in Cesarean Section or operative Vaginal Delivery rates
      3. Belfort (2015) N Engl J Med 373(7): 632-41 [PubMed]
      4. Neilson (2015) Cochrane Database Syst Rev (12): CD000116 [PubMed]
    5. References
      1. Visser (2015) Int J Gynecol Obstet 131(1): 25-9 [PubMed]
  • Interpretation
  1. Based on either method of auscultation (CEFM or SIA)
    1. CEFM: Graphical tracing of FHR and contractions
    2. SIA: Baseline and 60 sec before/after contractions
  2. Approach Mnemonic: DR C BRAVADO
    1. Determine Risk
      1. See Peripartum Risk to the Fetus
      2. Assign low, medium or high risk (see prenatal risk factors)
    2. Contractions
      1. Assess rate, rhythm, frequency, duration, intensity, and resting tone
      2. Normal
        1. Over a 30 minute period, averages <5 contractions per 10 minutes
      3. Suspicious: Tachysystole
        1. Over a 30 minute period, averages >5 contractions per 10 minutes
        2. Tachysystole increases risk of acidosis by not allowing recovery between contractions
          1. Uterine contractions normally transiently decrease uterine Blood Flow
        3. Intervene by stopping or slowing uterine stimulants (Oxytocin) or using Tocolytics
      4. Abnormal or Pathologic
        1. No change despite intrauterine Resuscitation and stopping Oxytocin or use of Tocolytics
        2. Associated with Category 2 or 3 FHT tracing (see below)
    3. Baseline Rate
      1. Normal: 110 to 160 bpm (based on 2 min segment within a 10 minute tracing)
      2. Suspicious
        1. Bradycardia (<110 bpm)
        2. Tachycardia (>160 bpm)
        3. Rising baseline (rate change persists >2 minutes)
      3. Abnormal or Pathologic
        1. Persistent Heart Rate <100 beats per minute
    4. Variability
      1. Normal
        1. Moderate variability is 6-25 bpm fluctuations from baseline over 10 minute period
      2. Suspicious
        1. Minimal variability is <6 bpm fluctuations from baseline over 10 minute period
        2. Marked variability is >25 bpm fluctuations from baseline over 10 minute period
      3. Abnormal or Pathologic
        1. Absent variability suggests decreased CNS Activity
        2. Sinusoidal pattern (undulating baseline pattern every 3-5 min for >20 minutes)
    5. Accelerations
      1. Normal
        1. Reassuring accelerations are >=15 bpm above baseline for 15 seconds (onset to peak <30 s)
          1. Preterm fetus will have accelerations >10 bpm for 10 seconds
        2. Prolonged accelerations last >2 minutes
        3. Baseline is considered changed when lasting >10 minutes
      2. Suspicious
        1. No accelerations are present
      3. Abnormal or Pathologic
        1. No accelerations despite scalp stimulation
    6. Decelerations
      1. Normal
        1. Early Decelerations (fetal head compression)
          1. Deceleration mirrors the contraction
          2. Deceleration nadir occurs at peak contraction
          3. Onset of Early Deceleration to nadir >=30 seconds
      2. Suspicious
        1. Variable Decelerations (cord compression)
          1. Onset of Variable Deceleration to nadir < 30 seconds
          2. Heart Rate decrease >=15 bpm
          3. Variable Deceleration Duration 15 seconds to 2 minutes
        2. Late Decelerations (uteroplacental insufficiency)
          1. Late Decelerations start after the contraction
          2. Onset to Late Deceleration nadir >=30 seconds
          3. Recurrent Late Decelerations occur with >50% of contractions in 20 minutes
          4. Prolonged Late Decelerations last >2 minutes
      3. Abnormal or Pathologic
        1. Late Decelerations that are recurrent or prolonged >30 min (>20 min if poor variability)
    7. Overall Assessment
      1. See Nonreassuring Fetal Status
      2. Normal
        1. No Hypoxia or acidosis
      3. Suspicious
        1. Low probability of Hypoxia or acidosis
        2. Correct reversible causes of of possible Fetal Hypoxia or acidosis
        3. Continue to monitor closely
      4. Abnormal or Pathologic
        1. High probability of Hypoxia or acidosis
        2. Immediate action to correct reversible causes of of possible Fetal Hypoxia or acidosis
        3. Expedite delivery
  • Signs
  • Reassuring or Normal (NICHD Category 1)
  1. Normal baseline (110-160 bpm)
    1. Moderate Fetal Bradycardia (100-120) may be present, but with good variability
  2. Good beat-to-beat variability (STV)
  3. Accelerations
    1. Heart Rate increases by 15-25 bpm over baseline
    2. Increase persists for 15-25 seconds
  4. Early Decelerations
    1. Suggests head compression with contraction
  5. Mild Variable Decelerations
  • Signs
  • Non-Reassuring or Indeterminate (NICHD Category 2)
  1. Fetal Tachycardia (>160)
  2. Absent or minimal beat-to-beat variability (STV)
  3. Prolonged decelerations
  4. Recurrent Late Decelerations but with maintained moderate variability
  5. Variable Decelerations with slow return to baseline (or overshoots baseline)
  6. Fetal Scalp Stimulation fails to result in accelerations
  • Signs
  • Ominous or Pathologic (NICHD Category 3)
  1. Sinusoidal Pattern
  2. Loss of variability AND
    1. Recurrent Late Decelerations
    2. Recurrent Variable Decelerations
    3. Fetal Bradycardia
  • Management
  1. See Nonreassuring Fetal Status
  • References
  1. Bailey (2000) ALSO, E:1-13
  2. Gabbe (2002) Obstetrics, p. 395
  3. (2009) Obstet Gynecol 114(1): 192-202 [PubMed]
  4. Arnold (2020) Am Fam Physician 102(3): 158-67 [PubMed]
  5. Bailey (2009) Am Fam Physician 80(12): 1388-98 [PubMed]
  6. Rylander (2001) Clin Fam Pract 3(2):287-305 [PubMed]